3Com CoreBuilder 9000, Руководство пользователя

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358 C
HAPTER
13: E
STABLISHING
ATM C
HANNELS
Signaling Protocol
Profile
In the CoreBuilder 9000 ATM Enterprise Switch, the signaling protocol
profile of a port defines the role that the port plays in the signaling dialog
with its attached ATM device. The profile can be either network or user .
When the CoreBuilder 9000 ATM Enterprise Switch port is connected to
an end station or edge device, the CoreBuilder 9000 Enterprise ATM
Switch port is normally defined as network (Net).
When the CoreBuilder 9000 ATM Enterprise Switch is connected to
another CoreBuilder 9000 ATM Enterprise Switch, the port of the
CoreBuilder 9000 ATM Enterprise Switch unit with the highest network
prefix is assigned the network profile and port of the other
CoreBuilder 9000 ATM Enterprise Switch is assigned the user (Usr) profile.
One difference between the two profiles is that the user initiates the ATM
connection by sending a SETUP message, but the network port defines
the VPI/VCI pair for the ATM connection. Thus, if an ATM user sends a
SETUP message to a CoreBuilder 9000 ATM Switch Fabric Module port,
the VPI/VCI message element is left empty. The switch proposes a VPI/VCI
pair for the connection and sends it back to the user as part of the CALL
PROCEEDING message or, in case there is none, as part of the CONNECT
message. (The CONNECT message is sent by the switch to the user only
after the switch has received a CONNECT message from the call
destination.)
Displaying the Signaling Protocol Profile
To display or update the signaling protocol profile, See “Update Signaling
Protocol Profile” on page 190.
Establishing a Virtual
Channel
Figure 17 shows the steps involved in establishing a virtual channel. In
steps
1, 2
(in Figure 17) an external link (connection) is set up by
signaling between the edge device and the switch. In step
3
an internal
link is set up by routing, and in steps
4
,
5
an external link is set up
between the switch and the edge device.
Point-to-Point Calls A point-to-point call is a collection of associated ATM VC or VP links that
connect two end points and enable data flow to and from both end
points.
Point-to-Multipoint
Calls
A point-to-multipoint call is a collection of associated ATM VC or VP links,
with associated end point nodes. A connection is defined as a section of a
call.